JP2015129442A - Saddle ride vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a saddle ride vehicle capable of accurately detecting that engine combustion is unstable.SOLUTION: If combustion is unstable in an engine 13 mounted in a motorcycle 1, a phenomenon occurs that an intake pressure of an internal negative pressure of an intake pipe 29 increases to be closer to the atmospheric pressure. A determination unit 77 can accurately determine that unstable combustion on the basis of a fluctuation in the internal pressure of the intake pipe 29 detected by an intake pressure sensor 65 for detecting the internal pressure of the intake pipe 29.

Description

  The present invention relates to a straddle-type vehicle in which a rider travels across a vehicle, and more particularly to a technique for detecting that combustion in an engine has become unstable.

  Environmental measures are required for saddle-type vehicles such as motorcycles that use an engine as a power source. Specifically, measures by improving exhaust gas purification performance, improving fuel efficiency, and the like can be mentioned. In such measures, it is important to determine the stability of combustion. That is, when the combustion becomes unstable, unburned gas is discharged as tail pipe emission, which affects both the exhaust gas purification performance and the fuel consumption. Therefore, by accurately detecting that the combustion has become unstable, it is possible to accurately control the combustion, leading to improved exhaust gas purification performance, improved fuel efficiency, and the like.

  As a factor that deteriorates the exhaust gas purification performance, for example, there is misfire. As a motorcycle (first device) that takes environmental measures by preventing this misfire, for example, there is a motorcycle that includes a crank pulse sensor and a misfire detection unit (see, for example, Patent Document 1). The crank pulse sensor detects the rotational speed of the engine. The misfire detection unit calculates the rotational speed of the engine based on the time interval of the crank pulse output from the crank pulse sensor, and detects misfire based on the difference between the rotational speeds at two predetermined crank angles.

  In the first device configured as described above, when the difference in engine speed exceeds a predetermined threshold, the misfire detection unit determines that misfire has occurred and restricts the operation of the engine. .

  By the way, in a motorcycle equipped with a catalyst, in order to activate the catalyst early, control is performed to increase the intake air amount and retard the ignition timing. In such control, if combustion becomes unstable due to product variation or misfire, etc., it is necessary to control to stabilize combustion by reducing the increase in intake air volume and advancing the ignition timing. It becomes.

  An example of such a control is an automobile that is not a straddle-type vehicle, but includes a rotation speed sensor, a crank angle sensor, and driving state determination means (see, for example, Patent Document 2). The rotational speed sensor detects the rotational speed of the engine. The crank angle sensor detects the angle of the output shaft. The operating state determining means determines the operating state of the engine based on output signals from the rotation speed sensor and the crank angle sensor.

  When the rotational speed change of the output shaft is larger than a predetermined value, the second device configured as described above determines that the operating state determining means is inferior in combustibility, and performs feedback control of the intake air amount. The combustion is prevented from deteriorating by performing control such as stopping the engine.

JP 2006-183502 A Japanese Patent No. 4742433

However, the conventional example having such a configuration has the following problems.
That is, a straddle-type vehicle such as a motorcycle has a characteristic that the fluctuation of the rotational speed of the engine is larger than that of an automobile even during normal times. Therefore, since it is difficult to distinguish between rotational speed fluctuation due to misfire or deterioration of combustibility and rotational speed fluctuation during normal operation, it is difficult to accurately detect that engine combustion has become unstable. There is.

  The present invention has been made in view of such circumstances, and by devising a method for detecting combustion instability, it is possible to detect that combustion of the engine has become unstable more accurately than before. An object is to provide a straddle-type vehicle that can be used.

In order to achieve such an object, the present invention has the following configuration.
That is, the invention according to claim 1 is directed to an engine having a combustion chamber, an intake pipe for introducing an air-fuel mixture into the combustion chamber, an air-fuel mixture that is attached to the intake pipe and is supplied to the combustion chamber. An air throttle valve for adjusting the amount, an intake pipe pressure detection unit for detecting an intake pressure in a region downstream of the air throttle valve in the intake pipe as an intake pipe pressure, and the engine based on fluctuations in the intake pipe pressure And a determination unit for determining that the combustion in has become unstable.

  [Operation / Effect] According to the first aspect of the present invention, when combustion instability occurs in the combustion chamber of the engine, the negative intake pressure in the downstream region of the air throttle valve in the intake pipe approaches the atmospheric pressure. The phenomenon of becoming higher occurs. Therefore, the determination unit can accurately determine that the combustion has become unstable based on the fluctuation of the intake pipe pressure detected by the intake pipe pressure detection unit.

  Moreover, in this invention, it is preferable that the said intake pipe pressure detection part is attached between the said air throttle valve and the said combustion chamber among the said intake pipes (Claim 2).

  Since the intake pipe pressure detector is attached between the air throttle valve and the combustion chamber, it is possible to accurately detect fluctuations in the intake pipe pressure adjacent to the combustion chamber.

  In the present invention, it is preferable that the air throttle valve is disposed above the engine.

  Since the air throttle valve is arranged above the engine, the distance to the combustion chamber can be shortened. As a result, the volume to be measured of the intake pipe pressure is reduced, and the sensitivity of fluctuations in the intake pipe pressure due to combustion instability can be increased, so that it is possible to accurately detect that combustion has become unstable.

  Moreover, in this invention, it is preferable that the said air throttle valve is arrange | positioned ahead of the rear end of the said engine by the side view (Claim 4).

  Since the air throttle valve is disposed in front of the rear end of the engine in a side view, the overall length of the engine can be suppressed and downsizing can be achieved.

  In the present invention, it is preferable that the air throttle valve is disposed between a front end and a rear end of the engine in a side view (Claim 5).

  Since the air throttle valve is disposed between the front end and the rear end of the engine as viewed from the side, the overall length of the engine can be suppressed and downsizing can be achieved.

  In the present invention, it is preferable that the volume of the intake pipe between the air throttle valve and the intake valve of the combustion chamber is smaller than the displacement of the engine.

  Since the volume between the air throttle valve and the intake valve of the combustion chamber is smaller than the engine displacement, the intake pipe has a smaller volume for measuring the intake pipe pressure. Therefore, since the sensitivity of fluctuations in the intake pipe pressure due to unstable combustion can be increased, it is possible to accurately detect that combustion has become unstable.

  In the present invention, the engine may include a cylinder inclined forward, and the air throttle valve may be disposed behind the cylinder and above the crankcase of the engine. Preferred (claim 7).

  Since the engine includes a cylinder inclined forward and the air throttle valve is disposed behind the cylinder and above the crankcase of the engine, the engine can be downsized.

  In the present invention, the engine includes a plurality of cylinders, and the intake pipe is provided for each cylinder, and a volume between the air throttle valve of each intake pipe and the intake valve of the combustion chamber is set. The engine displacement is preferably smaller than the displacement per cylinder of the engine.

  Since the engine includes a plurality of cylinders, an intake pipe is provided for each cylinder, and an air throttle valve is provided for each intake pipe, the volume to be measured for the intake pipe pressure is reduced. Therefore, since the sensitivity of fluctuations in the intake pipe pressure due to unstable combustion can be increased, it is possible to accurately detect that combustion has become unstable.

  In the present invention, the engine includes a single cylinder, the intake pipe is provided in the cylinder, and the volume of the air throttle valve in the intake pipe and the intake valve in the combustion chamber is determined by the exhaust of the engine. It is preferable that it is smaller than the amount (claim 9).

  Since the engine includes one cylinder, the intake pipe is provided in the cylinder, and the air throttle valve is provided in the intake pipe, the volume to be measured for the intake pipe pressure is reduced. Therefore, since the sensitivity of fluctuations in the intake pipe pressure due to unstable combustion can be increased, it is possible to accurately detect that combustion has become unstable.

  Further, in the present invention, a measurement pipe having one end connected in communication with each intake pipe and the other end connected by a collection section is provided, and the intake pipe pressure detection section is attached to the collection section of the measurement pipe. (Claim 10).

  An intake pipe pressure detection unit is attached to the collection part of the measurement pipe with one end connected to each intake pipe and the other end connected to the collection part. Can be measured. Therefore, cost can be suppressed.

  In the present invention, the engine includes an exhaust pipe for exhaust gas exhaust from the combustion chamber, the exhaust pipe includes a catalyst for purifying the exhaust gas, and activates the catalyst at an early stage. It is preferable to include a control unit that performs early activation control and suppresses or cancels early activation control when the determination unit determines that combustion is unstable (claim 11).

  When the engine includes a catalyst in the exhaust pipe, the control unit performs early activation control so that the catalyst can start the purification action in a short time. If the determination unit determines that combustion instability has occurred at this time, the control unit can suppress or stop the early activation control and start stabilization of combustion. Note that “suppressing early activation control” means lowering rather than completely stopping the temperature raising action of exhaust gas for early activation.

  In the present invention, it is preferable that the control unit starts the early activation control by increasing the amount of air introduced from the intake pipe or increasing the retard amount of the ignition timing in the combustion chamber ( Claim 12).

  When the control unit increases the amount of air introduced from the intake pipe, the ignition timing is retarded accordingly, the amount of fuel is increased, and the temperature of the exhaust gas is raised. Further, when the control unit increases the retard amount of the ignition timing, the air amount increases accordingly, the fuel is increased, and the temperature of the exhaust gas is raised. Any method can start early activation control.

  According to the straddle-type vehicle according to the present invention, when combustion instability occurs in the combustion chamber of the engine, a phenomenon occurs in which the negative intake pressure in the downstream region from the throttle in the intake pipe increases so as to approach the atmospheric pressure. Therefore, the determination unit can accurately determine that the combustion has become unstable based on the fluctuation of the intake pipe pressure detected by the intake pipe pressure detection unit.

1 is a side view showing an overall configuration of a motorcycle according to a first embodiment. 1 is a longitudinal sectional view of an engine of a motorcycle according to a first embodiment. 1 is a plan view of an engine of a motorcycle according to a first embodiment. FIG. 3 is a diagram illustrating a crank angle detection unit of the motorcycle according to the first embodiment. 1 is a block diagram including an ECU of a motorcycle according to a first embodiment. It is a graph which shows the example of a change of the intake pipe pressure at the time of normal. It is a graph which shows the example of a change of the intake pipe pressure at the time of misfire. It is the graph which changed the time axis in the graph of FIG. FIG. 6 is a side view showing an overall configuration of a motorcycle according to a second embodiment. 6 is a partial left side view including an engine of a motorcycle according to Embodiment 2. FIG. FIG. 6 is a side view showing an overall configuration of a motorcycle according to a third embodiment. Fig. 6 is a left side view showing a part of an engine of a motorcycle according to a third embodiment.

  A motorcycle will be described as an example of the saddle riding type vehicle in the present invention.

Embodiment 1 of the present invention will be described below with reference to the drawings.
FIG. 1 is a side view showing the overall configuration of the motorcycle according to the first embodiment related to the first embodiment.

  The motorcycle 1 in this embodiment includes a main frame 3, a front wheel 5, a rear wheel 7, a fuel tank 9, a seat 11, and an engine 13. The main frame 3 forms a skeleton of the motorcycle 1 and includes a head pipe 15 at the front and a rear frame 17 at the rear. The head pipe 15 is provided with a steering handle 19. The steering handle 19 is provided with a front fork 21 that is rotatably attached around the axis of the head pipe 15. The front fork 21 has a front wheel 5 rotatably attached to a lower end portion. The seat 11 is attached to an upper portion of the main frame 3 and an upper portion of a rear frame 17 extending rearward of the main frame 3. A fuel tank 9 is attached to the upper part of the main frame 3 behind the steering handle 19 and in front of the seat 11. The main frame 3 has an engine 13 mounted at the bottom. One end of the rear arm 23 is attached to the main frame 3 and the engine 13 so as to be swingable with respect to the main frame 3. The rear wheel 7 is rotatably attached to the other end portion of the rear arm 23. The rear wheel 7 is transmitted with the driving force of the engine 13 by a transmission mechanism 23 a disposed along the rear arm 23. An engine control unit 24 (hereinafter referred to as ECU) for controlling the engine 13 is mounted on the upper part of the main frame 3 and the lower part of the fuel tank 9.

  Here, the engine 13 will be described with reference to FIGS. 2 is a longitudinal sectional view of the engine of the motorcycle according to the first embodiment, and FIG. 3 is a plan view of the engine of the motorcycle according to the first embodiment. In FIG. 2, the right direction (cylinder head 37 direction) corresponds to the front of the motorcycle 1, and in FIG. 3, the upward direction (cylinder head 37 direction) corresponds to the front of the motorcycle 1.

  The engine 13 according to the present embodiment is a parallel 4-cylinder. The engine 13 includes a crankcase 25, a cylinder 27, an intake pipe 29, and an exhaust pipe 31. The crankcase 25 supports a crankshaft 33, and a cylinder 27 and a cylinder head 37 are attached to the upper part of the crankcase 25. The cylinder 27 includes a piston 39 that can linearly reciprocate. The piston 39 is connected to the crankshaft 33 by a connecting rod 41, and the linear reciprocating motion of the piston 39 is converted into the rotational motion of the crankshaft 33. The cylinder 27 is provided in a posture inclined forward (rightward in FIG. 2) with respect to the crankcase 25. The cylinder head 37 forms a combustion chamber 43 by the cylinder 27 and the piston 39. The cylinder head 37 includes an intake port 45 and an exhaust port 47 that communicate with the combustion chamber 43. An intake valve 49 that opens and closes the combustion chamber 43 is attached to the intake port 45, and an exhaust valve 51 that opens and closes the combustion chamber 43 is attached to the exhaust port 47. The exhaust pipe 31 connected to the exhaust port 47 is provided with a catalyst CA at a site away from the exhaust port 47. The catalyst CA purifies the exhaust gas discharged from the combustion chamber 43 through the exhaust port 47 into the exhaust pipe 31 by a chemical reaction.

  One end of the intake pipe 29 is connected to the intake port 45 in communication. The other end of the intake pipe 29 is connected to the air cleaner 53. Air is sucked into the intake port 45 via the air cleaner 53. A fuel injector 55 is attached to the intake pipe 29. The fuel injector 55 injects fuel based on the injection signal calculated and sent by the ECU 24. A throttle 57 is attached upstream of the fuel injector 55 in the intake pipe 29. The throttle 57 is provided with a throttle valve 59 (air throttle valve) for adjusting the amount of intake air in the intake pipe 29.

  The throttle 57 is disposed above the engine 13, and is disposed behind the cylinder 27 (leftward in FIG. 2) and above the crankcase 25 when the engine 13 is viewed from the side. Further, the throttle 57 is disposed forward of the rear end of the engine 13 when the engine 13 is viewed from the side. Since the throttle 57 is arranged at such a position, the distance to the combustion chamber 43 can be shortened. Accordingly, the volume to be measured for the intake pipe pressure is reduced, and the sensitivity of fluctuations in the intake pipe pressure due to instability of combustion can be increased. Therefore, the responsiveness until combustion instability can be detected can be increased.

  The throttle 57 may be configured such that the throttle valve 59 and the intake pressure sensor 65 are integrally formed.

  As shown in FIG. 3, the engine 13 includes a measurement tube 61. One end of the measuring tube 61 is connected to each intake pipe 29 through an opening 62, and the other end of the measuring tube 61 is connected to one collecting portion 63. One end of the measurement pipe 61 is connected between the throttle 57 and the combustion chamber 43 in the intake pipe 29. One intake pressure sensor 65 is attached to the collective portion 63 in order to detect pressure. The intake pressure sensor 65 detects an intake pressure between the intake valve 49 and the throttle valve 59 in each intake pipe 29 as an intake pipe pressure. The intake pipe pressure measured by the intake pressure sensor 65 is output to the ECU 24. Since the intake pressure sensor 65 is attached between the throttle 57 and the combustion chamber 43 in each intake pipe 29 via the measurement pipe 61, the intake pressure sensor 65 can be made compact.

  The intake pressure sensor 65 described above corresponds to the “intake pipe pressure detector” in the present invention.

  The engine 13 of the motorcycle 1 in the present embodiment is a four-cylinder engine having a displacement of about 1300 cc. The total volume from the throttle valve 59 to the intake valve 49 of the throttle 57 of each cylinder is about 400 cc to 600 cc. That is, the volume from the throttle valve 59 to the intake valve 49 of the throttle 57 in each intake pipe corresponding to each cylinder is smaller than the exhaust amount per cylinder of the engine 13.

  The concept of how to obtain the displacement of the engine 13 and the volume of the intake pipe 29 described above is as follows. In the case of the engine 13 having a multi-cylinder structure in which the throttle valve 59 is provided for each cylinder, the volume from the throttle valve 59 to the intake valve 49 is obtained. In the case of the engine 13 having a multi-cylinder structure in which only one throttle valve 59 is provided and the intake pipe 29 is branched, the volume of the common portion of the intake pipe 29 is divided by the number of cylinders, and the intake pipe 29 After the bifurcation portion, the volume is obtained for each cylinder. However, when the engine 13 has multiple cylinders, the total displacement and the total intake pipe volume may be compared, or the exhaust amount per cylinder and the intake pipe volume may be compared.

  Reference is now made to FIG. FIG. 4 is a diagram illustrating a crank angle detection unit of the motorcycle according to the first embodiment.

  A crank angle detector 67 is disposed inside the crankcase 25 in the right direction. The crank angle detection unit 67 includes a signal rotor 69 and a sensor 71. The signal rotor 69 is mounted in the crankcase 25 so as to rotate around the rotation axis P in conjunction with the rotation of the crankshaft 33. The signal rotor 69 has a disk-like appearance and has teeth 69a formed so as to protrude from the outer peripheral surface. The signal rotor 69 in this example includes a total of 11 teeth 69 a, and each tooth 69 a is formed around the rotation center P of the signal rotor 69 at an angle of 30 °. However, the tooth 69a corresponding to the 12th tooth is not formed at a position 30 ° from the 11th tooth 69a, and this portion is a missing tooth portion 69b. By detecting the missing tooth portion 69b, it is possible to accurately determine the timing at which the piston 39 becomes top dead center.

  The sensor 71 is composed of, for example, a pickup coil. When the signal rotor 69 rotates, the distance between each tooth 69a and the sensor 71 changes, so that a pulse-like signal is output from the sensor 71 for each tooth 69a excluding the missing tooth portion 69b. This signal is a crank angle signal.

  Please refer to FIG. FIG. 5 is a block diagram including the ECU of the motorcycle according to the first embodiment.

  The ECU 24 includes a data processing unit 73, a determination unit 77, a threshold storage unit 79, and an engine control unit 81. The data processor 73 receives the crank angle signal output from the sensor 71 of the crank angle detector 67 and the intake pipe pressure signal output from the intake pressure sensor 65, and associates the crank angle with the intake pipe pressure. .

  The threshold storage unit 79 stores in advance a threshold for determining that the combustion of the engine 13 has become unstable. The determination unit 77 determines whether the combustion of the engine 13 has become unstable based on the processing value of the intake pipe pressure output from the data processing unit 73 and the threshold value in the threshold value storage unit 79. When it is determined that the combustion has become unstable, the determination unit 77 causes the engine control unit 81 to perform control for stabilizing the combustion. The engine control unit 81 receives a throttle opening signal from a throttle opening sensor (not shown), receives a rotation speed signal of the engine 13 from a rotation speed sensor (not shown), controls the engine 13, and determines a determination unit. In accordance with an instruction from 77, control for stabilizing combustion in the engine 13 is performed.

  In addition to the control for stabilizing the combustion, the engine control unit 81 performs control of the engine 13 during normal operation and early activation control of the catalyst CA when the engine 13 is started. Control of the early activation of the catalyst CA, for example, delays the ignition timing in the combustion chamber 43 and increases the amount of air introduced from the intake pipe 29. Thus, by increasing the air amount, the retard amount of the ignition timing is increased, the fuel is increased, the exhaust gas is heated, and the catalyst CA is activated.

  Note that, for early activation control, the retard amount of the ignition timing in the combustion chamber 43 may be increased instead of increasing the air amount. Thus, by increasing the retard amount of the ignition timing, the amount of air is increased, the amount of fuel is increased, the exhaust gas is heated, and the catalyst CA is activated.

  Next, a variation example of the intake pipe pressure in the engine 13 will be described with reference to FIGS. FIG. 6 is a graph showing an example of fluctuations in the intake pipe pressure during normal operation, FIG. 7 is a graph showing an example of fluctuations in the intake pipe pressure at the time of misfire, and FIG. 8 is a time chart in the graph of FIG. It is the graph which changed the axis.

  As shown in FIG. 6, when the engine 13 is operating normally, the engine 13 is a four-cycle engine and includes four cylinders 27. An explosion occurs in the combustion chamber 43, and four waves (variations in the negative pressure direction) occur in the intake pipe pressure in a crank angle range of 720 °. The fact that the engine 13 is in a normal operation state can also be seen from the fact that the engine speed in this graph is substantially constant.

  On the other hand, as shown in FIG. 7, when one of the four cylinders 27 of the engine 13 misfires due to unstable combustion, only three waves are applied to the intake pipe pressure in the crank angle range of 720 °. Does not occur. The fact that the engine 13 is unstable due to misfire can also be seen from the fact that the engine rotation speed in this graph has decreased by about 200 rpm from around the four waves where the intake pipe pressure has disappeared.

  FIG. 8 is a graph in which the time axis in the graph of FIG. 7 is changed. From this graph, it can be determined that the intake pipe pressure has increased by appropriately setting the threshold value. .

  When combustion instability occurs in the engine 13 as described above, the rate of change of the rotational speed in the engine 13 increases, and accordingly, the negative intake pipe pressure in the region downstream of the throttle 57 in the intake pipe 29. The inventors have found that a phenomenon occurs in which the pressure increases as it approaches the atmospheric pressure. By utilizing this phenomenon, it is possible to accurately determine that the combustion has become unstable based on the detected fluctuations in the intake pipe pressure without using the rate of change in the rotational speed of the engine 13. The inventor found out.

  The determination unit 77 described above determines whether combustion is unstable based on the processing value of the intake pipe pressure and a preset threshold value. As the processing value, for example, a value obtained by averaging processing such as a moving average value or a weighted average of the intake pipe pressure may be used, or the intake pipe pressure may be used as it is. There are various data processing methods, and a plurality of processing methods may be used in combination.

  Note that the above-described determination of combustion instability is preferably not performed at the time of starting or when the opening degree of the throttle 57 is changed by the rider because the determination accuracy may be lowered. That is, the intake pipe pressure cannot be measured stably until the opening of the throttle 57 and the fluctuation of the rotational speed of the engine 13 converge within a certain range. Therefore, in order to prevent erroneous determination, it is preferable that the determination unit 77 does not determine combustion instability until a predetermined time for the intake pipe pressure to stabilize has elapsed.

  Also, early activation control of the catalyst CA may be performed at the time of starting. In this case, the engine control unit 81 performs control to increase the amount of air from the intake pipe 29 more than usual and retard the ignition timing. If it is determined that combustion instability is determined during the early activation control of the catalyst CA, the engine control unit 81 operates the throttle valve 59 of the throttle 57 in the closing direction, and the ignition timing. Control is performed to stabilize combustion by advancing. That is, the early activation control of the catalyst CA is suppressed or stopped. Suppressing the early activation control here means not stopping the temperature raising action of the exhaust gas completely for early activation but reducing the temperature raising action of the exhaust gas. When the ignition timing is controlled according to the air amount, the ignition timing is advanced in accordance with this by reducing the air amount. When the amount of air is controlled according to the ignition timing, the amount of air is reduced accordingly by advancing the ignition timing. As described above, when the air amount and the ignition timing are controlled in conjunction with each other, if only one of the target values is controlled, both the air amount and the ignition timing are controlled.

  According to the present embodiment, when combustion in the engine 13 becomes unstable, a phenomenon occurs in which the negative intake pressure in the intake pipe 29 increases so as to approach the atmospheric pressure. Therefore, the determination unit 77 can accurately determine that the combustion has become unstable based on the fluctuation of the intake pipe pressure detected by the intake pressure sensor 65.

  In addition, since the volume of the throttle 57 from the throttle valve 59 to the intake valve 49 is smaller than the displacement of the engine 13 in the above-described combustion instability determination method, it is easy to catch fluctuations in the intake pipe pressure due to combustion instability. It is suitable for the motorcycle 1.

Next, Embodiment 2 of the present invention will be described with reference to the drawings.
FIG. 13 is a side view showing the overall configuration of the motorcycle according to the second embodiment, and FIG. 14 is a partial left side view including the engine of the motorcycle according to the second embodiment.

  The motorcycle 1A according to the present embodiment is a scooter type in which a rider rides with both feet on the floor. The motorcycle 1A includes a main frame 3, a front wheel 5, a rear wheel 7, a fuel tank 9, a seat 11, an engine 13, a head pipe 15, a steering handle 19, and a front fork 21. Yes.

  In the engine 13 of the motorcycle 1A, the cylinder 27 is deeply inclined forward to near horizontal. The engine 13 has an intake pressure sensor 65 attached directly downstream of the throttle 57 in the intake pipe 29. The throttle 57 is disposed above the engine 13, is disposed in front of the rear end of the engine 14 in a side view, and is disposed between the front end and the rear end of the engine 13. Note that the intake pressure sensor 65 may be attached to the intake pipe 29 via the measurement pipe 61 as in the first embodiment.

  In the motorcycle 1A in this embodiment, the intake pipe pressure and the crank angle from the intake pressure sensor 65 are given to the ECU 24, and the combustion stability of the engine 13 can be accurately determined by the above-described method.

  The engine 13 of the motorcycle 1A in the present embodiment is a single cylinder engine having an engine displacement of about 115 cc. The volume from the throttle 57 to the intake valve 49 is about 50 cc to 80 cc. That is, the volume from the throttle 57 to the intake valve 49 is smaller than the displacement. Even the engine 13 having such a small displacement produces the same effect as that of the first embodiment.

Next, Embodiment 3 of the present invention will be described with reference to the drawings.
FIG. 15 is a side view showing the overall configuration of the motorcycle according to the third embodiment, and FIG. 16 is a left side view showing a part of the engine of the motorcycle according to the third embodiment.

  The motorcycle 1B in the present embodiment is the same type as that of the first embodiment described above, but has a smaller displacement compared to the first embodiment. The motorcycle 1B includes a main frame 3, a front wheel 5, a rear wheel 7, a fuel tank 9, a seat 11, an engine 13, a head pipe 15, a steering handle 19, and a front fork 21. Yes.

  In the engine 13 of the motorcycle 1B, an intake pressure sensor 65 is directly attached to the intake pipe 29. The throttle 57 is disposed above the crankcase 25 of the engine 13, disposed in front of the rear end of the engine 14 in a side view, and disposed between the front end and the rear end of the engine 13. Note that the intake pressure sensor 65 may be attached to the intake pipe 29 via the measurement pipe 61 as in the first embodiment.

  In the motorcycle 1B according to the present embodiment, the intake pipe pressure and the crank angle from the intake pressure sensor 65 are given to the ECU 24 as in the first and second embodiments, and the combustion of the engine 13 is stabilized by the method described above. Can be accurately determined.

  The engine 13 of the motorcycle 1B in the present embodiment has an exhaust amount of about 250 cc, and a volume from the throttle 57 to the intake valve 49 is about 100 cc to 150 cc. That is, the volume from the throttle 57 to the intake valve 49 is smaller than the displacement. Thus, the engine 13 having an intermediate displacement between the first embodiment and the second embodiment has the same effects as the first and second embodiments.

  The present invention is not limited to the above embodiment, and can be modified as follows.

  (1) In the first to third embodiments described above, the motorcycles 1, 1 </ b> A, 1 </ b> B provided with the engine 13 of four cylinders 27 (four cylinders) and one cylinder 27 (single cylinder) have been described as an example. However, the present invention is not limited to the motorcycles 1, 1A, 1B equipped with such an engine 13. For example, the present invention can be applied to a motorcycle provided with an engine 13 having two cylinders 27 (two cylinders) and three cylinders (three cylinders). Further, it is not necessary that the cylinders 27 are arranged in parallel, and the present invention can be applied regardless of the type as long as the engine 13 includes the combustion chamber 43 such as a V-shaped arrangement or a horizontally opposed arrangement.

(2) In the first embodiment described above, the case where the predetermined range of the crank angle is 6 points (crank angle 360 °) has been described as an example when the moving average value of the intake pipe pressure is obtained. However,
Since the number of intake pipe pressure fluctuations in one cycle varies depending on the number of cylinders 27 of the engine 13, the predetermined range of the crank angle is preferably determined by the number of cylinders 27. By doing so, the difference between the intake pipe pressure when the combustion is unstable and the intake pipe pressure when the combustion is stable can be stabilized, so that the determination of the combustion instability can be stabilized.

  (3) In Examples 1 to 3 described above, it is determined that combustion instability is determined based only on the intake pipe pressure. However, in addition to the intake pipe pressure, the conventional pulse output of the rotational speed sensor is detected, and even if combustion instability is determined based on the fluctuation of the intake pipe pressure and the fluctuation of the rotational speed of the engine good. Thereby, combustion instability can be detected with higher accuracy.

  (4) In the first embodiment described above, the four-cylinder engine 13 has been described as having an equally spaced explosion, but the present invention can also be applied to an engine 13 having an unequally spaced explosion.

  (5) In the first to third embodiments described above, the motorcycles 1, 1 </ b> A, 1 </ b> B on which riders ride as straddle-type vehicles have been described as examples. However, the present invention is not limited to such a kind of saddle-ride type vehicle. (Buggy) and snowmobiles can also be applied.

1, 1A, 1B ... Motorcycle 3 ... Main frame 13 ... Engine 24 ... ECU
25 ... Crankcase 27 ... Cylinder 29 ... Intake pipe 31 ... Exhaust pipe 33 ... Crankshaft 37 ... Cylinder head 43 ... Combustion chamber 49 ... Intake valve 51 ... Exhaust valve 55 ... Fuel injector 57 ... Throttle 59 ... Throttle valve 61 ... Measuring pipe 62 ... Opening 63 ... Collecting part 65 ... Pressure sensor 67 ... Crank angle detection part 69 ... Signal rotor 69a ... Teeth 69b ... Missing tooth part 71 ... Sensor 73 ... Data processing part 77 ... Determination part 79 ... Threshold storage part 81 ... Engine control Part

Claims (12)

An engine with a combustion chamber;
An intake pipe for introducing an air-fuel mixture into the combustion chamber;
An air throttle valve attached to the intake pipe for adjusting the amount of air-fuel mixture supplied to the combustion chamber;
An intake pipe pressure detection unit that detects an intake pressure in a region downstream of the air throttle valve in the intake pipe as an intake pipe pressure;
A determination unit that determines that combustion in the engine has become unstable based on fluctuations in the intake pipe pressure;
A straddle-type vehicle equipped with. The saddle riding type vehicle according to claim 1, wherein
The intake pipe pressure detection unit is a straddle-type vehicle that is mounted between the air throttle valve and the combustion chamber in the intake pipe. The saddle riding type vehicle according to claim 1 or 2,
The air throttle valve is a straddle-type vehicle disposed above the engine. The saddle riding type vehicle according to any one of claims 1 to 3,
The air throttle valve is a straddle-type vehicle disposed in front of a rear end of the engine in a side view. The saddle riding type vehicle according to any one of claims 1 to 4,
The air throttle valve is a straddle-type vehicle that is disposed between a front end and a rear end of the engine in a side view. The saddle riding type vehicle according to any one of claims 1 to 5,
The intake pipe is a straddle-type vehicle in which the volume between the air throttle valve and the intake valve of the combustion chamber is smaller than the displacement of the engine. The saddle riding type vehicle according to any one of claims 1 to 6,
The engine includes a cylinder with a posture inclined forward,
The straddle-type vehicle, wherein the air throttle valve is disposed behind the cylinder and above the crankcase of the engine. The saddle riding type vehicle according to claim 6,
The engine includes a plurality of cylinders,
The intake pipe is provided for each cylinder,
A straddle-type vehicle in which a volume between the air throttle valve of each intake pipe and an intake valve of the combustion chamber is smaller than an exhaust amount per cylinder of the engine. The saddle riding type vehicle according to claim 6,
The engine includes one cylinder,
The intake pipe is provided in the cylinder;
A straddle-type vehicle in which the volume of the air throttle valve of the intake pipe and the intake valve of the combustion chamber is smaller than the displacement of the engine. The saddle riding type vehicle according to claim 8,
One end portion is connected to each of the intake pipes, and the other end portion is provided with a measurement pipe connected at a collecting portion,
The intake pipe pressure detection unit is a straddle-type vehicle attached to a collective part of the measurement pipe. The saddle riding type vehicle according to any one of claims 1 to 10,
The engine includes an exhaust pipe for discharging exhaust gas from the combustion chamber,
The exhaust pipe includes a catalyst for purifying exhaust gas,
A straddle-type vehicle that performs early activation control for early activation of the catalyst and includes a control unit that suppresses or cancels early activation control when the determination unit determines that combustion is unstable. The saddle riding type vehicle according to claim 11, wherein
The control unit is a straddle-type vehicle that starts the early activation control by increasing the amount of air introduced from the intake pipe or increasing the retard amount of the ignition timing in the combustion chamber.

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